was__in 1950__this happened?A)it,when B)that,that C)it,that D)that,in which

题目

was__in 1950__this happened?A)it,when B)that,that C)it,that D)that,in which

答案

选A 因为这是个疑问句所以看起来有点蒙人,我们把他换成陈述句：
()was in 1950()this happened.
前面空要填it来作为形式主语,因为后面有个时间状语从句,后面空要填when因为有时间在前面用来引导时间状语从句.